Already known in the state of the art, in particular according to WO 2008/102093, is a motor vehicle exhaust valve, of the type comprising: a support including an exhaust gas passage opening; a plug that is able to tilt between a plugging position and a position freeing the passage; and an elastic strip for returning the plug to its plugging position. The elastic strip has a first end fastened to the support and a second end bearing on the plug. The second end is able to slide on the plug between a first position, in which the plug is in its plugging position, and a second position, in which the plug is in its release position.
Such a valve is steered by the exhaust gas that circulates in the exhaust line, as a function of the flow rate of said gas. In fact, this gas generates a thrust force on the plug, opposite a return force generated by the elastic return strip. When the flow rate of the gas is high enough, the thrust force is greater than the return force, with the result that the plug goes into its release position to allow the passage of the gas through the passage opening.
Said valve has both an acoustic, noise reduction function and a permeability function. Thus, for optimal effectiveness, the valve should remain closed when the exhaust gas flow rate is low to ensure a relatively low noise level, and the valve should open quickly and significantly when the gas flow rate is greater to facilitate the passage of the exhaust gas, and so as not to hinder the proper operation of the engine.
In general, a valve of the state of the art does not make it possible to perform these two functions perfectly. For example, if the stiffness of the elastic strip is too high, therefore generating a high return force, the valve remains in its plugging position at a low gas flow rate, but does not open with a large enough angle at a high flow rate. However, if the stiffness of the elastic strip is too low, therefore generating a low return force, the valve opens correctly at a high flow rate, but generally also opens for a low gas flow rate for which it should remain in the plugged position.